Packaging machines are generally known in which a continuous web of material is converted into a plurality of individual pouches. The continuous web of material is folded in half over a plow to form two continuous side panels joined by a bottom fold. The folded web is passed through a series of seal bars which form transverse seals between the side panels, thereby forming a strip of pouches interconnected by transverse seals. A cutter cuts through each transverse seal to form individual pouches with unsealed top edges. The individual pouches are transferred to a pouch filler, filled with product, and sealed. The sealed pouches are then collected for transport. Machines of this type may be categorized as either horizontal or vertical machines, depending on the general direction of web travel. The present invention relates to horizontal packaging machines in which the web travels horizontally.
The type and volume of product being packaged often determines whether the packaging process should use a continuously or intermittently advancing web. Certain products, such as hard candy, require a fill based on weight instead of volume. Scale fillers require relatively long periods to fill a pouch. As a result, slower cycle continuous motion or intermittent motion is required to provide additional fill time. In addition, larger volume fills require more time, and therefore intermittent motion through the filler may be necessary. More free flowing products, such as sugar, may be dispensed using a diving funnel suitable for filling continuously advancing pouches.
In light of the above, packaging machines have been developed specifically for either intermittent or continuous operation. Continuous motion machines typically require web-engaging components which are moveable and can be phased with the advancing web. For example, U.S. Pat. No. 5,722,217 to Cloud discloses a packaging machine for use with a continuously advancing web. The '217 device uses a sealing drum to form the vertical seals of the pouches. Sealing wires are circumferentially spaced about the sealing drum to provide sealing points. The web is entrained about the drum and the drum is rotated so that seals are formed as the web continuously advances. The '217 device further fills the pouches while they are still connected and therefore the web must be continuously advanced through the pouch filler section as well. It is not seen, however, that the '217 device is operable with an intermittently advancing web since it would be difficult to control the sealing drum so that it starts and stops at the appropriate times.
Most conventional intermittent motion machines, on the other hand, have web-engaging components which are stationary and perform operations during dwell periods between incremental advances. For example, U.S. Pat. No. 5,181,365 to Garvey, et al. discloses a packaging machine for use with an intermittently advancing web. The '365 device has sealers and a cutter spaced longitudinally along the web path at fixed locations. These components perform their associated operations during web dwells. Accordingly, machines such as that disclosed in the '365 patent are not suitable for use with a continuously advancing web since the stationary components would stretch or tear the web during operation.
Changing a machine over from continuous to intermittent web motion, or vice versa, is further limited by the conventional mechanical line shafting used in such machines. Most previous packaging machines use a drive line with an array of gearboxes and/or cams to operate the various components. To switch between continuous and intermittent operation would require substantial modifications to the drive line to enable it to run in the other mode.